This invention relates to a polyethersulfone composition, a method to synthesize the polyethersulfone composition and articles made from the composition.
Polyethersulfones are a commercially important family of high performance, high temperature amorphous thermoplastics. These polymers are of interest to many industries because of their combination of high heat resistance, hydrolysis resistance in steam and hot water environments and good overall chemical resistance. Another reason these polymers are of great commercial interest is because in addition to offering the stated high performance attributes, they are also transparent, unlike most semi-crystalline materials which are also used in high temperature applications.
Polyethersulfones can be produced by a variety of methods. For example, U.S. Pat. Nos. 4,108,837 and 4,175,175 describe the preparation of polyarylethers and in particular polyarylethersulfones. U.S. Pat. No. 6,228,970 describes the preparation polyarylethersulfones with improved polydispersity and lower amounts of oligomers. British patent GB 1,264,900 teaches a process for production of a polyethersulfone comprising structural units derived from 4,4′-biphenol, bisphenol-A (4,4′-isopropylidenediphenol), and 4,4′-dichlorodiphenylsulfone.
The transparency of polyarylethersulfones makes them suitable for use in a variety of applications such as lids and covers for surgical and dental instrument sterilization trays which have to undergo steam autoclave sterilization. In the application just mentioned, the contents of the sterilization trays may by virtue of the transparency of the polyethersulfone, be inventoried by visual inspection without exposing the contents to the environment. Other uses and potential uses of polyethersulfones include pet transport containers, and dairy processing equipment, particularly milking machine components. Food and beverage applications also include uses such as coffee serving carafes and containers, microwave cookware, covers for cookware containers, and doors and windows for appliances, such as rotisserie grills. The inherent flammability resistance and low smoke release characteristics of polyethersulfones, particularly those of polyetherphenylsulfone, enhance the utility of such polymers in applications such as mass transit where low heat release on combustion and low toxic smoke emission properties of components used in passenger compartments are of critical concern. In the aircraft industry, in particular, the low flammability and low smoke attributes of polyethersulfones make such materials suitable for use in a variety of aircraft cabin interior components.
While the currently available polyethersulfones typically possess intermediate heat resistance, it would be desirable to improve their heat resistance while still maintaining or improving their impact properties. This would improve the utility of these polymers in a number of applications, especially in applications such as automotive headlight reflectors, medical trays, aircraft cabin interior components, consumer oriented hot food or beverage service items like tableware and baby bottles, pet transport containers, surgical trays, coffee serving carafes, cookware containers, where improving impact resistance at higher temperatures would be highly desirable. It is axiomatic that the deficiencies of currently available materials are tolerated because viable alternatives are lacking. Key areas for improvement in order to maximize the utility of polyethersulfones are; physical/mechanical integrity at high temperatures, hot water resistance, resistance to cleaning agents, and chemical inertness of the resin under conditions of use.
Commercially important polyarylethersulfones include polysulfone (PSU), polyphenylsulfone (PPSU) and polyethersulfone (PES). PSU is a well-known high temperature amorphous engineering thermoplastic resin exhibiting a glass transition temperature (Tg) of about 185° C., high strength, stiffness and toughness over a temperature range of from about −100° to 150° C. PSU has an Izod impact strength value (Notched Izod value) of about 69 Jm−1 (1.3 ft-lb/in). PSU was commercially introduced in 1965 by the Union Carbide Corporation and is commercially available as UDEL® polysulfone from Solvay Advanced Polymers LLC. Another versatile polyarylethersulfone polymer is polyphenylsulfone (PPSU). PPSU is commercially available from Solvay Advanced Polymers LLC under the trademark of RADEL®. It has a Tg of 220° C. and an Izod impact strength value of about 700 Jm−1 (13 ft-lb/in).
In various applications it would be highly desirable to produce polyarylethersulfones with higher glass transition temperatures (i.e. increased heat resistance) relative to known polyethersulfones, while maintaining or improving the high impact strength typically exhibited by materials of the polyethersulfone class. In order to achieve higher heat resistance in polyethersulfones having excellent impact strength, improvements in the design of the polyethersulfone compositions are necessary.